The invention relates to a hammer drill, in particular a percussion hammer comprising a tool holder, an air cushion striking mechanism including a piston displaceable in a guide tube and a striker, and a device which holds the striker in its front position facing the tool holder by venting the air cushion, when the hammer is idle. In a hammer known from DE-PS 26 41 070, a fixed guide tube in which the piston and striker are guided so as to be tight and sliding, is enclosed by a control body which is axially displaceable for idling control. The control body embraces the guide tube at the front in such a way that a collar of the intermediate anvil contacts the base of the control body and the latter can accordingly be pushed axially inward during hammer operation. Such a construction has the disadvantage that it is only suitable for pure chisel hammers, but not for drill hammers with rotary drive. A rotary drive of the guide tube is not possible, and the rotating movement can also not be transmitted to the tool holder, since the control body prevents the connection of the guide tube with the tool holder. Moreover, the additional control body brings about an increased cost in manufacturing and is a hindrance when the hammer is to be supplemented with further functions.